The present invention relates to a process for the selective removal of bismuth and/or antimony from a sulfuric acid solution in which bismuth and/or antimony are dissolved together with other metals.
In the purification and refining of nonferrous metals, it is unavoidable that a variety of metals are admixed into the product as impurities due to the diversity of ores used as raw materials. Among such impurities are also included bismuth and/or antimony. In particular, in the purification and refining of copper, it is substantially difficult to remove such impurities completely by the pyrometallurgical process. Accordingly, bismuth and/or anitomy, though small in quantity, are almost always contained in a copper anode and are submitted to a subsequent electrolytic purification step. Further, the electrolytic purification of copper is generally carried out in an aqueous sulfuric acid solution and thus part of the bismuth and/or antimony contained in the copper anode is dissolved into said aqueous solution during the electrolysis, with the result that the concentration thereof gradually increases. Moreover, the bismuth and/or antimony thus-dissolved deposit on a copper cathode in accordance with the increased concentration so that the concentration of bismuth and/or antimony is generally maintained at approximately 0.3-0.5 g/l in the aqueous sulfuric acid solution used as the electrolyte.
As a means of controlling the concentration of bismuth and/or antimony in the above aqueous sulfuric acid solution, there have been employed the neutralization method, the sulfiding method, the electrolytic collection method using an insoluble anode and the like, to which a portion of said aqueous solution (or copper electrolyte) removed from the system is submitted.
However, since the copper electrolyte generally contains approximately 200 g/l of free sulfuric acid, approximately 50 g/l of copper ion, approximately 5 g/l of arsenic, approximately 3 g/l of iron and the like, it has been difficult by the above methods to remove bismuth and/or antimony from said copper electrolyte in an efficient and selective manner.
The present inventors have made an intensive investigation into a process for the effective removal of only bismuth and/or antimony from an aqueous sulfuric acid solution containing dissolved bismuth and/or antimony, together with other metals, such as a copper electrolyte. As a result, it was found that bismuth and/or antimony were removed selectively from the above aqueous sulfuric acid solution by allowing said solution to contact with a phosphomethylamino chelate resin. The present invention has been completed on the basis of this discovery.
In this connection, a process (Japanese Patent Laid-Open No. 177420/1983, published on Oct. 18, 1983) has been proposed relating to the removal of indium from an aqueous acidic solution containing indium by allowing said aqueous solution to contact with an aminomethylenesulfonic acid derivative. However, no technique has been known for the selective removal of bismuth and/or antimony dissolved in an aqueous acidic solution using a phosphomethylamino chelate resin.